*{
    margin: 0;
    padding: 0;
}
body{
    background-color: #000;
    display: flex;
    justify-content: center;
    align-items: center;
    width: 100vw;
    height: 100vh;
}
ul{
    width: 60vw;
    display: flex;
    justify-content: space-between;
    align-items: center;
}
li{
    list-style-type: none;
}
a{
    position: relative;
    color: #fff;
    text-decoration: none;
    padding: 10px 20px;
    transition: background-color 0.8s;
}
a:hover{
    background-color: orangered;
}
a:before{
    position: absolute;
    content: "";
    width: 20px;
    height: 20px;
    border: 2px solid orangered;
    border-width: 0 0 2px 2px;
    left: 0;
    bottom: 0;
    opacity: 0;
    transition: 0.2s;
}
a:after{
    position: absolute;
    content: "";
    width: 20px;
    height: 20px;
    border: 2px solid orangered;
    border-width: 2px 2px 0 0;
    top: 0;
    right: 0;
    opacity: 0;
    transition: 0.2s;
}
a:hover:before{
    left: -10px;
    bottom: -10px;
    opacity: 1;
}
a:hover:after{
    top: -10px;
    right: -10px;
    opacity: 1;
}